1. Field of the Invention
The present invention relates to an exhaust heat recovery system for recovering exhaust heat discharged from an internal combustion engine.
2. Description of the Related Art
In an exhaust heat recovery system described in JP-A-3-128719, an auxiliary heating is performed for an air conditioner by using exhaust heat from an engine. The exhaust heat recovery system is provided with a heat pipe that includes an evaporation portion (heat receiving portion) at one end, and a condensing portion (heat radiating portion) at the other end. The evaporation portion is located in an exhaust gas passage of the engine, and the condensing portion is located adjacent a heater core in an air conditioning case of the air conditioner. The heater core heats air passing therethrough by using engine coolant (hot water) in a water circuit as a heating source.
Generally, the temperature of exhaust heat is rapidly increased as compared with the temperature of engine coolant at an initial time immediately after an engine start. In the exhaust heat recovery system, the heating operation of the air conditioner is performed by using the exhaust gas, so as to improve a rapid heating performance in the air conditioner. However, in the above exhaust heat recovery system, the heat recovered in the exhaust heat of the engine is only used for heating air in the air conditioner in the winter, and thereby it is difficult to effectively use the exhaust heat from the engine.